champion

Champion, one who combats or fights; specifically, in the Middle Ages, a person who took up the cause and fought in the place of another. Single combat was one of the ways frequently adopted to decide the right of a cause; and women, children, or aged persons were allowed to appear by a representative. At one time
the champions were looked upon as disreputable, being ready, for hire, to take up any quarrel. At a later period, however, during the ages of chivalry, the champion was a knight, who entered the lists on behalf of an injured lady, a child, or one incapable of self-defense. The word is also applied to one who earns, or claims, the preeminence in feats of physical prowess, or skill.

One who engages in any contest; esp. one who in ancient times contended in single combat in behalf of another's honor or rights; or one who acts or speaks in behalf of a person or a cause; a defender; an advocate; a hero.

A stouter champion never handled sword.
Shak.

Champions of law and liberty.
Fisher Ames.

2.

One who by defeating all rivals, has obtained an acknowledged supremacy in any branch of athetics or game of skill, and is ready to contend with any rival; as, the champion of England.

⇒ Champion is used attributively in the sense of surpassing all competitors; overmastering; as, champion pugilist; champion chess player.